A lighting device for a household appliance, in this case, for example, for a baking oven or a refrigerator, is described in German Utility model G 86 02 774.3, where light source is provided which is disposed on the side wall and separated from the treatment chamber by a glass pane. The light source is surrounded by a reflector means to direct the light beams into the treatment chamber. A similar such device is described for a baking oven German Utility model G 86 09 316.9. In this variant, the light sources are disposed above the treatment chamber, and the light beams are radiated into the treatment chamber through so-called “light-guiding channels”. European Patent Publication EP 0 446 692 describes a further lighting device which is for use in a refrigerator and is provided with a tubular light guide. In that approach, the light radiation is introduced into the refrigeration compartment through a rod-shaped light carrier made of glass or plastic into the treatment chamber, the light source being mounted outside of the treatment chamber.
Another lighting device for the treatment chamber of a household appliance is described in European Patent Publication EP 0 922 910. The embodiment disclosed therein has so-called “light channels” which are disposed on the side walls of the treatment chamber and allow introduction of light beams from a light source located in the upper portion of the treatment chamber. The light beams are deflected toward the treatment chamber by reflection means disposed one above the other in the light channel, thus illuminating different levels in the treatment chamber.
German Patent Publications DE 103 18 860, DE 103 18 859 and DE 103 18 861 also describe a similar lighting device for a cooking appliance. The embodiment described therein is also provided with reflection means which are disposed at different levels in channels in the region of the door and which allow light beams to be reflected at different levels. The light channel is designed such that the extent of the reflection means, at least in one direction transverse to the light beams emitted by the light source toward the reflection means, increases with increasing distance of the respective reflection means from the light source and in such a manner that part of the light beams reach the more distal reflection means in an unhindered manner.
These lighting devices have the problem that they do not provide for optimum illumination of the treatment chamber, especially as the amount of light radiation introduced is not optimally used. Another reason for this is that these lighting devices for household appliances only use special light sources of low efficiency.